As is well known in the art, silicone rubber adhesive compositions are generally classified into the addition and condensation curing types. Compositions of the condensation curing type are known to cure at room temperature and firmly adhere to various plastic members, but take a long time to complete curing and are thus unsuitable for the manufacture of electronic parts requiring efficient mass production. Compositions of the addition curing type are suited for the manufacture of such parts because of high curing rate, but are less adhesive to plastics. For curing, they require heating to 100.degree. C. or higher temperature with the risk of heat distortion of plastics.
Many attempts have been made to improve the adhesion of silicone rubber adhesive compositions of the addition curing type. For example, Japanese Patent Publication (JP-B) No. 13508/1978 discloses compounds having a hydrogen atom directly attached to a silicon atom and an oxirane group in their molecule, JP-B 21026/1978, 23354/1970 and 46783/1988 disclose compounds having a trialkoxy group, and JP-B 26376/1983 discloses compounds having a trialkoxy group, an oxirane group and a hydrogen atom directly attached to a silicon atom in their molecule, all teaching that these compounds are effective for improving adhesion. However, adhesive compositions having these compounds blended therein were unsuccessful in achieving sufficient bonding force at low temperatures. Moreover, JP-B 8854/1977 discloses alkoxysilane compounds having an amino group as effective for adhesion improvement. Regretfully, when these compounds are blended in silicone rubber compositions of the addition reaction type, the compositions are less shelf stable either in two- or one-part form because of the presence of amino group.